GB2100818A - Drain rods - Google Patents

Abstract

Drain rods 10, 12 made of plastics material integrally moulded screw threads at each end, male at one end 18 and female at the other, so that a series of such rods can be connected together to provide the required length. In order to prevent the screw threads becoming detached, particularly when the material is soft because of an elevated temperature, they are reinforced by stiffening material 14, 20, which are preferably steel tubes moulded into the plastics material in the course of manufacture. <IMAGE>

Description

SPECIFICATION Drain rods This invention relates to drain rods (also used for chimney sweeping) which customarily consists of about 3 foot lengths of rod provided with a male threaded connector at one end and a female threaded connector at the other end, so that the rods can be screwed together and likewise screw connected to a cleaning auger, brush or other implement.

Drain rods were for many years made of bamboo or like cane having a certain flexibility, and with a machined brass connecting portion fixed to each end. In more recent years, the cane has been replaced by a suitable plastics material having an even greater flexibility.

Proposals have been made to cheapen these articles e.g. in British Patent 2075624A particularly by eliminating the brass connections.

In experiments made by the present inventor, attempts have been made to form the screwthreaded portion out of the plastics material in a moulding process, but certain difficulties are encountered. One of the reasons for using the plastics material is its inherent deformability enabling the length of rod to snake around the possibly convoluted path of a drain, and the same property creates a risk of the screwthreaded parts being disengaged inadvertently, in which event instead of the drain rods clearing an obstruction, they will constitute an additional obstruction left in the drain.A further problem with these plastics materials is that (because they are thermoplastic and not thermosetting) they soften at elevated temperatures, and in hot summer conditions or for certain export markets a screwthreaded joint which was perfectly satisfactory on an English winter's day may become quite unsatisfactory.

The object of the present invention is to provide improvements enabling integrally moulded screwthreaded joints to be made in plastics drain rods, but avoiding these problems.

In accordance with a first aspect of the invention, considered broadly, at least one of the ends of a plastics drain rod having an integrally moulded screwthreaded coupling portion, is reinforced by a stiffer material.

The stiffening material made be steel and preferably is in the form of a steel tube or sleeve which is moulded into the plastics material in the course of manufacture.

By the term "moulded in" is meant an arrangement in which the steel (or other metal part or other stiffening) is substantially totally enclosed by the plastics material, and preferably is completely and wholly enclosed by the plastics material. The distinction is that in the substantially enclosed version, an edge or a face of the metal component is exposed and possibly is visible, whereas in the other version the metal is completely surrounded by plastics material so that it is not visible in the finished article.

It will be appreciated that to mould in, it is necessary to locate the stiffening portion within the forming mould. In the first possibility, where the metal is only substantially enclosed, a portion of the metal is available to be located in the mould structure, possibly by interengaging portions, possibly by magnetic clamping of the steel part to the mould face or possibly by the use of a spigot or peg projecting from the mould wall and which contacts the stiffening sleeve at a number of points so as to locate it whilst the plastics is formed around the metal.

In an alternative possibility where the metal is to be wholly surrounded by the plastics, it is preferred to carry out the manufacture in two stages. In a first stage the metal component has a plastics component added to it and that plastics component may be located in the mould wall in similar fashion to that referred to hereinbefore, but so as to space the metal reinforcement from the mould wall, whilst the injection or other forming process proceeds.

In one possibility, a plain steel tube is used as the reinforcement, selected so as to be of a suitable external diameter so that when moulded within and concentrically of a male threaded portion the roots of the screwthreads so moulded as spaced from the wall by a minimum thickness of the plastics. That tube may have a plastics plug inserted into one end or moulded into one end as the preliminary step, so that the plug can be gripped or located in a bore in the mould wall whilst the forming process proceeds, and at the conclusion of the moulding step the whole of the tube and a portion of the plastics plug which originally projected from the tube will be surrounded by and effectively fused to the formed plastics component i.e. the end portion of the drain rod.The portion of the original peg which remains may project from the end of the screwthreaded portion (and in forming the complementary screwthreaded portion on the end of another rod a recess may be provided for it) or it may be severed before use.

The screwthreaded portion is preferably formed immediately adjacent to a plain cylindrical portion and which terminates in a shoulder between that portion and the rod proper. This in the case of the male threaded portion. The female threaded end of the rod may be similarly formed but with a plain cylindrical bore portion at its free end and to cooperate with the said pilot portion on the male end, as well as with the complementary female screwthreads. The end face of the female end is then intended to abut the shoulder at the male end when the parts are screwed together tightly. The tubular metal liner preferably extends over substantially the whole length of the screwthreaded portion and also (according to a feature of the invention) over the pilot portion and indeed may also extend beyond the shoulder and into the rod proper.

As an alternative to using a plain tubular reinforcement sleeve, the sleeve may have a plain tubular portion integrally formed with a radially extending collar or flange, and that flange may be located at the extreme end face of the coupling, that is at the end of the screwthread remote from the rod (particularly in the case where the metal is only substantially wholly enclosed, and in this case the moulded plastics material will extend up to one face of the radial flange, but the other face of the radial flange will be bare. Alternatively, the radial flange may be buried in the largest diameter portion of the coupling between the screwthreaded portion and the rod proper.

Where only one end of the rod is to be reinforced with a stiffening component, it is preferred to reinforce the male threaded portion rather than the female threaded portion.

According to another aspect of the invention, the female threaded end of a drain rod is moulded integrally and of the same plastics material as the rod and with the required female screwthreads, and the said female end also has a generally parallel sided socket formed inwardly of the rod from the said female screwthreads and opening thereto; whilst the male end of the rod is provided with a metal reinforcing pin mounting a rotatable male threaded component generally in the manner illustrated in Figure 4 of our published application number 2024357A.Whilst this version is essentially more expensive than the arrangements previously described in which both ends of the rod are integrally moulded with screwthreads, it has the advantage of reducing costs in avoiding the necessity for the separate metal component as of Fig. 2 of the said published application whilst retaining some of the advantages in terms of lockable connections.

An illustrative embodiment of the invention is now more particularly described with reference to the accompanying drawing in which the sole figure is a sectional fragmentary view showing a pair of plastics drain rods screwed together.

In the drawing, the rod 10 has its female end connected to the male end of the rod 12. Both of these ends are reinforced by steel tubes. The tube 14 is wholly embedded in and wholly surrounded by the material of the rod 10, having been prepared in a previous operation by being moulded into an annulus of material which has later been located in an annular recess in the mould wall when when rod 10 was formed. The annulus of material may be the same material as used for the rest of the moulding so that in the ordinary course of plastics moulding it will fuse to the remainder of the moulding and become integral therewith. The notional joint line between the original part and the part formed in the final manufacturing step is shown by the broken line 16.Thus as seen in the figure, the right hand portion of the female end of the rod, that is the extreme end adjacent the aperture which receives the male end of the rod 12, is the fused part which supported the steel tube 40 during the moulding of the drain rod part 10.

Similarly in the case of the male screw threaded end 18. This is reinforced by the steel liner 20 which was supported in the die during the formation of the rod 12 by the annular portion 22 which had previously been moulded around an end of the tube 20.

In the drawing it will be seen that the steel tubes 14 and 20 are the same length and coextensive in the assembled condition. This is not essential, but the purpose of the stiffening is essentially to improve the security of the screw connected joint and minimise possibilities of the parts becoming inadvertently detached. It may be that in practice inserts of sufficient diametric rigidity could be of relatively short length and located for example more closely adjacent to the joint 24 between the adjacent end faces of the two rods, to have the same effect.

It will also be noted that the drawing shows the mouldings being substantially tubular. This shows the possibility of forming the screw threaded end portion, or finally forming the screw threaded end portions, from generally preformed tube-like rod, for example by setting the end portions to create the larger diameter parts in a process analogous to forging, which is for convenience included within the term "integrally moulded" used herein. These words are therefore to be inserted as meaning that the screw threads are essentially made of the same material as the length of the rod and without any joint between the two, that is between the rod and the screw threaded portion, in the finished product. Whether the screw threads were made at the same time as the rod or separately, and whether made out of the length of the rod, or separately and effectively joined by the fusing or like technique is immaterial.

Claims (6)

1. A plastics drain rod has a male screw threaded portion at one end and a female screw threaded portion at the other end and is characterised in that at least one of the screw threaded portions is reinforced by a stiffer material.

2. A drain rod as claimed in Claim 1 wherein the reinforcement is a metal tube or ring.

3. A drain rod as claimed in Claim 1 or Claim 2 wherein the reinforcement is a steel tube substantially surrounded by the plastics material.

4. A drain rod as claimed in any preceding claim wherein only one end of the rod is so stiffened.

5. A drain rod as claimed in Claim 1 wherein the male end of the rod is provided with a metal reinforcing pin mounting a rotatable male threaded component as shown in patent application 2024357A.

6. A drain rod substantially as described with reference to the accompanying drawings.